• Heat the oven to 375℉. Prepare a 9-inch springform pan and spray with nonstick cooking spray. Set aside. 

Make The Streusel Topping

• Combine all the streusel topping ingredients into a small mixing bowl. Use your clean hands, a fork, or a pastry blender to combine everything together until you have a thick crumb mixture. Set aside for later. 
  1 cup granulated sugar, 1/4 cup light brown sugar, 1/3 cup + 3 tablespoons all-purpose flour, 1/2 teaspoon ground cinnamon, 6 tablespoons butter

Make The Blueberry Coffee Cake

• In a large bowl, add the flour, granulated sugar, softened butter, milk, egg, baking powder, and salt. Use an electric hand mixer to beat everything together until combined and forms a smooth batter.
  2 cups all-purpose flour, 3/4 cup granulated sugar, 4 tablespoons butter, 3/4 cup whole milk, 1 large egg, 1 tablespoon baking powder, ½ teaspoon salt
• Add the blueberries and very gently stir just until they are combined into the batter.

  ^{* You don't want to mix too hard or else the fresh berries will burst and bleed into the batter.} 
  2 cups fresh blueberries
• Evenly spread the coffee cake batter into the prepared pan. Sprinkle the streusel topping evenly over top the batter. 
• Bake for 55-65 minutes. The coffee cake will be puffed up and a toothpick inserted into the middle should come out with dry tender crumb on it. The edges of the cake will be golden brown and slightly pulled away from the pan.

  ^{* If the top is getting too browned then loosely lay a piece of foil over top the coffee cake for the last several minutes of the bake time.}
• Remove the coffee cake from the oven and allow it cool for 20 minutes at room temperature. Loosen the edges of the cake from the pan using a butter knife and then unhook and remove the sides of the springform pan. 

Make The Glaze

• Combine all the glaze ingredients in a small bowl and mix together until desired consistency is reached. Add more or less, or more or less powdered sugar, to achieve a pourable consistency or a thicker more spreadable consistency.
  1/2 cup powdered sugar, 1-2 teaspoons whole milk, ¼ teaspoon vanilla extract
• Serve the coffee cake warm or let it cool to room temperature before serving.